IV - Extra » History » Version 11
Version 10 (COLIN, Tony, 12/15/2015 10:23 PM) → Version 11/15 (COLIN, Tony, 12/16/2015 03:07 PM)
h1. IV - Extra
{{>toc}}
h2. 1. CubeSat performances.
h3. 1.1 Measurement of encoding/decoding time.
h4. 1.1.1 In simulation.
POSIX requires that CLOCKS_PER_SEC equals 1000000 independent of the actual resolution.
p=. !Clock1.png!
*1000 ticks per milliseconds*
p=. !Clock2.png!
*Time measurement of data encoding*
p=. !Clock3.png!
*Printing clock data*
p=. !Time_RS_resized.PNG!
*Chart of Reed Solomon time measurement*
h4. 1.1.2 With Floating-Point OPeration (FLOP)
p=. !FLOPs2.png!
Hence, encoding stands for *O(nbytes x NPAR)* with _nbytes_ is the codeword length, _NPAR_ the number of parity bits.
Since it is a systematic code _nbytes = information_word_length + NPAR_ encoding stands for *O(information_word_length)* with NPAR constant.
Note that a more accurate way would be to consider processor speed and Salvo function OSGetTiks :
p=. !OSGetTiks.PNG!
h3. 1.2 Busy memory on CubeSat.
p=. !Memory.png!
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h2. 2. Current topics.
For the purpose of reliability for Land Mobile Satellite (LMS) channel, a solution is discussed about error correcting code on the Transport layer [1]. Regarding new trends of erasure codes related to satellites [2], an efficient way to perform encoding over LMS channel is to consider _Non-Binary codes_ such as Reed-Solomon code (studied in [[III - Advanced Project]] chapter) or Non-Binary LDPC code (which is highly complex to implement). The Non-Binary characteristic would be to consider a whole packet or a sliced packet as a symbol in order to decrease the error probability of packets.
A possible continuity to this project could be to integrate the OpenFEC code available on "OpenFEC - Downloads":http://openfec.org/downloads.html in the CubeSat Kit. This would be easily done by following chapter [[II - Tutorial - Simple project on CubeSat Kit|II - Tutorial]] and [[III - Advanced Project|III - Advanced Project]] that could be a integration pattern for any CubeSat project.
Research papers proposed on IEEE Website :
[1] "Transport layer coding for the land mobile satellite channel":http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1391458&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1391458
[2] "Erasure Codes for Space Communications: Recent Findings and New Challenges":http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6333092&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6333092
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{{>toc}}
h2. 1. CubeSat performances.
h3. 1.1 Measurement of encoding/decoding time.
h4. 1.1.1 In simulation.
POSIX requires that CLOCKS_PER_SEC equals 1000000 independent of the actual resolution.
p=. !Clock1.png!
*1000 ticks per milliseconds*
p=. !Clock2.png!
*Time measurement of data encoding*
p=. !Clock3.png!
*Printing clock data*
p=. !Time_RS_resized.PNG!
*Chart of Reed Solomon time measurement*
h4. 1.1.2 With Floating-Point OPeration (FLOP)
p=. !FLOPs2.png!
Hence, encoding stands for *O(nbytes x NPAR)* with _nbytes_ is the codeword length, _NPAR_ the number of parity bits.
Since it is a systematic code _nbytes = information_word_length + NPAR_ encoding stands for *O(information_word_length)* with NPAR constant.
Note that a more accurate way would be to consider processor speed and Salvo function OSGetTiks :
p=. !OSGetTiks.PNG!
h3. 1.2 Busy memory on CubeSat.
p=. !Memory.png!
---
h2. 2. Current topics.
For the purpose of reliability for Land Mobile Satellite (LMS) channel, a solution is discussed about error correcting code on the Transport layer [1]. Regarding new trends of erasure codes related to satellites [2], an efficient way to perform encoding over LMS channel is to consider _Non-Binary codes_ such as Reed-Solomon code (studied in [[III - Advanced Project]] chapter) or Non-Binary LDPC code (which is highly complex to implement). The Non-Binary characteristic would be to consider a whole packet or a sliced packet as a symbol in order to decrease the error probability of packets.
A possible continuity to this project could be to integrate the OpenFEC code available on "OpenFEC - Downloads":http://openfec.org/downloads.html in the CubeSat Kit. This would be easily done by following chapter [[II - Tutorial - Simple project on CubeSat Kit|II - Tutorial]] and [[III - Advanced Project|III - Advanced Project]] that could be a integration pattern for any CubeSat project.
Research papers proposed on IEEE Website :
[1] "Transport layer coding for the land mobile satellite channel":http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1391458&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1391458
[2] "Erasure Codes for Space Communications: Recent Findings and New Challenges":http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6333092&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6333092
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